It is often necessary or desirable, in various industrial applications, to treat solids-laden aqueous fluids to remove the solids and recover substantially clean water for re-use. A particular example is found in drilling operations in the petroleum industry, where water and water-based fluids are commonly used as drilling fluids (or drilling “muds”), for purposes including cooling of the drill bit and removing drill cuttings from the well bore. The drilling fluid is injected down the drill stem and exits through the drill bit, and then is forced to the ground surface through the annular space between the drill stem and the well bore, carrying excavated material (i.e., cuttings) to the surface in suspension. The “used” fluid is then processed to remove the suspended solids, which are then disposed of, leaving substantially clean water than can be re-used in the well, or used for other purposes.
There are various known methods and apparatus for removing solids from aqueous fluids, involving the use of some combination of settling tanks, mechanical agitation, chemical treatment (e.g., using precipitation-enhancing agents such as coagulants and flocculants), and/or mechanized transport of settled or precipitated solids. The present invention teaches an improved apparatus and method for removing suspended solids from aqueous fluids, using lower amounts of coagulants and flocculants than known systems, and without requiring conveyors or other mechanized means for transporting settled or precipitated solids from the apparatus.